shop-talk supported in part by Fat Chance Garage
http://fatchancegarage.com
At 08:11 PM 11/8/2005, Richard Beels wrote:
> 1. A phone line does carry some good juice on it - 70-ish V DC
> when ringing, iirc. Wouldn't want that in the tub with me if it
> was an older, "real" phone (pre-breakup).
It's worse than that. The "battery voltage" is around 48 - 50VDC
when the line is idle. The ring voltage is 110VAC. It will knock
you on your butt! T-1 circuits have 130 to 150VDC.
If you ever happen to work on a business phone system with message
waiting lights on analog phones, those lights are speced for 90VAC,
but many phone systems drive them with the ring voltage which is even
higher. If you're working on a field of punch downs on such a
system, probably 10% of the phones will have an active MWL and the
accompanying high voltage. Be careful!
-Wayne
|